The A/C is 100% FOR SURE used to cool the HV battery pack, and at a very modest temperature. In fact, my research and testing shows the A/C is used to cool the battery pack any time the battery is over 30'C ( 86'F ).

Now, between 30'C and 33'C ( 92'F ) the engine will cycle on and off to allow EV mode. If the battery pack exceeds 33'C, then the engine will run at stoplights, just to cool the battery. I find this helpful to know.

So parking in the sun is definately BAD for fuel economy, as the engine will need to run and burn more gas to cool the Battery. ( It chills down pretty quick though. )

-John

P.S. for proof, look under the rear bumper, driver side, for two silver lines ( pipes ).
One is cooling feed, the other is cooling return to compressor. The compressor is run from a belt attached to the gasoline engine.